Articles for uses such as garments or for protective packaging are frequently elasticized to provide a sealed tight fit. Among the various types of garments using elastic means to provide a sealed fit are disposable garments such as disposable diapers which are often sealed in the leg area to prevent leakage of body excretions. There has also been an increased interest in sealing the waist area of disposable diapers for the same purpose.
There are several ways that articles may be elasticized. These include the sewing of elastic into the substrate material which is to form the article, adhering the elastic onto the substrate material, and utilizing a heat shrinkable elastic which is bonded to the article and shrunk by the application of heat to an elastic form which permits the elastic extension and contraction of the substrate. Sewing of elastic into disposable articles is presently seldom used due to its complexity and slowness and resulting high cost. Adhering of the elastic onto a substrate material is commonly used, but nevertheless has its drawbacks. These include the difficulty of handling the elastic in a stretched form, particularly when it is applied in a direction transverse to the direction of movement of a moving substrate material. When elastic is glued to a substrate material in a relaxed condition, it is necessary to first corrugate the substrate material so that it will have excess material with can be extended to stretch the elastic and provide the elasticization effect. The need to corrugate the substrate material also complicates this approach, particularly when the elastic is applied in a direction transverse to the direction of a moving substrate material. Heat shrinkable elastic is applied in a relaxed form and, because it will gather the substrate material with it when it is caused to shrink, it is not necessary that the substrate material first be corrugated. The application of the heat shrinkable elastic in a relaxed form and the elimination of the need to corrugate the substrate material simplifies this approach considerably. However, the temperature level required to shrink the heat shrinkable elastic is above the tolerance level of some substrate materials commonly used in making disposable garments, particularly polypropylene and polyethylene films, and so it is difficult to use heat shrinkable elastic with these substrates. Moreover, heat shrinkable elastics often do not retain a sufficient amount of their elastomeric properties when heated and they thus are frequently unsuitable for many elasticization purposes.